He was jailed for 14 years at Peterborough Crown Court on Thursday (20 October).

The court heard how shortly before the "frenzied one-sided attack" at HMP Peterborough on 9 December, Palmer had complained of feeling unwell and rang a buzzer from his cell.

A prison officer told him to drink some water and said a nurse would be along shortly.

"I asked him [Palmer] if he had taken any 'spice', which is like a drug that's taken in prison," the officer told the trial. "He replied 'I don't know'. It did make me quite suspicious. Normally, if they have not taken it, they would reply 'no'."

The officer said he made eye contact with Ojuederie at the time, who was awake on the bottom bunk and "seemed fine". But 12 minutes later, Palmer rang the intercom again to say: "I'm sorry, I don't know what happened."

The prison officer returned to find Palmer swaying from side to side in his cell and covered in blood. His cellmate, Ojuederie, was lying on the floor with "horrific injuries" and foam coming out of his mouth. He was pronounced dead at the scene.

Palmer, who was serving six years for grievous bodily harm (GBH), was arrested on suspicion of murder. He told officers: "I don't know what happened".

The two-and-a-half week trial into the killing had heard how Palmer was Ojuederie's "only friend" in the jail, and that there was no evidence of any grudge or dispute between the pair.

The defendant said he wasn't a user of Spice, but that Ojuederie was. He claimed in the moments leading up to the attack he had either accidentally inhaled the drug through secondary smoke, or had smoked a spiked cigarette without realising, the Peterborough Telegraph reported.

Abbas Lakha QC, defending, said while it was not disputed his client had killed Ojuederie, it was possible Palmer had involuntarily used the drug spice and the effects of this might have led him to launch the attack.

The prevalence of Spice and other synthetic drugs in prisons across the country has been blamed for fuelling rising violence behind bars. The problem has become so pronounced the government has toughened punishments for those caught smuggling or throwing the psychoactive drugs into prisons.

Detective Chief Inspector Adam Gallop, from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit, said he accepted the jury's verdict that the killing was manslaughter.

'A frenzied one-sided attack'

He said: "The attack was one of the most vicious I have seen, and happened at a time when Terry Ojuederie was unable to defend himself or escape.

"I can only say as some small consolation that in all probability Terry would have lost consciousness very quickly. On the evidence presented during the trial, the jury has found Palmer guilty of manslaughter on the grounds of diminished responsibility and I respect that decision."

A statement from Ojuederie's family described the killing as a "frenzied one sided attack by his cellmate".

It thanked the jury for its verdict, saying: "We dreaded the possibility that Terry's killer may escape punishment should his defence be successful.

"Nothing can bring Terry back to us or take away the pain and devastation we are living with each day.

"We are left instead with an emptiness and the horror of his final moments as heard in detail during this murder trial. The bitter feeling at how this could happen in prison, a place we thought Terry would be safe, will remain with us forever, as will the torment of not knowing for sure the truth of what really happened in his cell that night."

It added: "Terry was kind, caring and loving. He was very sociable and always tried to see the best in people.

"Given that he was the only person with Terry in the cell, Palmer had no choice but to admit to ferociously killing Terry. Despite that we have had to endure a long trial with what seemed at times a real possibility that he could walk free, an outcome that would have left us feeling angry and confused."